Mig Welder
If you are new to using gas, open the valve on the cylinder slowly, and then all the way. Do not just open it a turn or so. Open the valve fully, and then make sure you close it when you turn your welder off. If you are doing sheetmetal, I recommend 0.23 wire instead of the more common 0.30. The smaller wire doesn't need as much heat and is a little easier to control. Plus less heat equals less chance of warping things.
Garry